Fire dampers for meeting building and fire codes are well known. Typically, they allow air flow therethrough in normal conditions, but automatically close in the event of a temperature rise above a prescribed level during a fire, to block smoke, heat, and the fire itself from freely flowing through the ductwork in engulfing the building. Most often, dampers of this type are held in an open position by various kinds of heat responsive linkages, but which automatically snap shut under biasing forces of a spring(s) or gravity once the threshold temperature is exceeded. In such installations, the fire dampers of this type usually involve frame-mounted enclosures inserted directly into the various conduit systems in the building. To the front of the frame-mounted enclosure is a register or grill diffuser serving as a supply or an exhaust vent, either with or without the ability to regulate the volume of air flowing through it.
Although these types of fire dampers have been around for years, only with the recent adoption of more stringent building and fire codes has attention been directed to their ability to optimally perform during fire emergencies. For example, with the frame mounted enclosure seated directly into a conduit of the building, back from its overlying register or grill, an air space exists through which the fire can shoot, even before the flames reach the damper blades closed off by the action of the melting heat responsive, or bi-metallic linkage. Secondly, and were this not bad enough, a further problem exists where the depth dimension forming the shaft between the fire rated sheet-rock construction wall is insufficient to fully house the frame-mounted enclosure, so that the register or grill, along with the front of the damper frame extend inwardly of the room--a condition outside the requirements of the various building and fire codes which apply. And, even beyond that, the problem becomes even more magnified where the fire damper employs an opposed blade damper behind it, at its rear, in serving as a screwdriver adjustable air diffuser. Experience has shown that many times, where one even strives to comply with the building and fire codes to minimize these problems, efforts must be taken at the construction site itself to specially make, one-by-one, individual assemblies to meet the installation requirements, thereby increasing labor and manufacturing costs, in an arrangement that does not, and probably will not, obtain Underwriters Listing approval.